As a main component of a hand drier, a blower comprises a centrifugal impeller and a motor for driving the impeller. The impeller moves air to form a pressurized airflow that is discharged via an air outlet. Hand driers and vacuum cleaners typically employ a centrifugal blower with a central air inlet and a peripheral air outlet.
Referring to FIG. 1, a conventional centrifugal impeller has a base plate 10, a cover plate 20, and a blade assembly 30 arranged between the base plate 10 and the cover plate 20. A motor shaft mounting hole 101 is formed at a central position of the base plate 10. An air inlet 201 is formed at a central position of the cover plate 20. The blade assembly 30 includes a plurality of curved blades 301 arranged annularly. Cover plate mounting portion 302 and base plate mounting portion (not shown) extent outwardly from a top side (close to the cover plate) and a bottom side (close to the base plate) of each curved blade 301, respectively. The cover plate 10 and the base plate 20 have rectangular blade mounting holes 202 and blade mounting holes (not shown) corresponding to the cover plate mounting portions 302 and base plate mounting portions (not shown), respectively.
One drawback of the conventional blower is that, when the motor speed is high, especially higher, than 33000 RPM, it is known for the centrifugal impeller to break. Basically, cracks occur in the cover plate, spreading out from the blade mounting holes 202 close to the air inlet 201. The cracks lead to the failure of the centrifugal impeller, reducing the lifespan of the blower.